Stray elimination in radioreceivers



May 19, 1925. 1,537.975A

'F. K. vREl-:LAND

STRAY ELIMINATION IN RADIOBEGEIVHRS Filed Aug. e; 1919 ,3 sheets-Shen 14 Cp La v I 74er L11 v 5 JU .5'

q. l 6,1/ K l IV a T- l Uf L l A 7i S Z I #Cf v Cs JD s May 19, 1,925.1,537,975

y K. VREELAND STRAY ELIMINATION IN RADIORECEIVERS Filed Aug. 6, A1919 3Sheets-Sheet 2 May 19,A 1925. 11,537,975

F. KQ VREELAND STRAY ELIMINATION IN RADIORECEIVERS Filed Aug, 6,l :19195 Sheets-Sheet 5 described a 'reame May i9, i925.

UNTED STATES FREDERICK K. VREELAND, or MoN'rcLAIR, NEW JERSEY.

STRAY ELIIINATION IN' RADIORECEIVERS.

Application led August 6, 1919. Serial No. 315,651.

T 0 all whom t may concern.'

Be it known that I, FREDERICK K. VREE- LAND, a citizen of the UnitedStates, resid ing at'Montclair, countyvoflEsscx, State of N eW Jersey,have invented certain new and' useful Improvements in Stray Eliminationin Radioreceivers, of Which'thefollowing is a specification.

The invention, herein described relates to an improvement in receivingsystem for radio intelligence, whereby interference by strays,atmospheric or artificial, is eliminated or minimized.

In my U. S. Patent No. 1,315,584, I have receiving system among otherfeatures a baffle circuit which permits the .ready passage of impulsesof signal frequency but opposes the passage of st-rays, combined with aby-pass element or elements whereby stray impulses are diverted frqm thereceiver and dissipated.

lIn my U. S. Patent No.- 1,407,103, I havedescribed a system includingan intensity selector `in combination With a baille circuit whereby thediversion of strays and undiminished reception of signal impulses ispromoted.

The present invention utilizes the basic principles of the formerapplications together'with additional features directed particularly tothe elimination of atmospheric l i' I' strays of sudden, impulsivecharacter. Ide- 'sire also to claim specically certain features thatwere set forth in the former applica tions but not specifically claimed.

complex system such as that described in the first named patent,including a plusignal frequency, vcombined with a pluralityy 4 0 .ralityof baffle elements eachv tuned to the of by-pass elements, the partsbeing. suitably proportioned in the manner set forth, is.

highly effective intransinitting freely cur; rents of a given frequencyand in diverting and absorbing the energy vof currents of r otherfrequencies. To securesharp discrimination between dierent frequencies,the impedance of the Joy-pass' should be smallv with respect to thecapacity and inductance re; actances of theba'tlle elements. The by-passimpedance may be either a pure resistance,

a capacity reactance or an inductance reactance, ora combination ofthese. If, Vthe bypass reactancexis made too large, the system includingwill transmit frequencies on either side of the signal frequency. On theotherhand, the by-pass impedance is made larger. than the equivalentresistance of the shunted portion to prevent undue shuntingof the signaliinpulses. The system is thus highly effective in excluding interferencefrom signals of foreign frequency, and largely effective in excludingatmospheric strays.

The use of an intensity selector in the by pass element, as set forth inthe second patent above named, greatly increases the efficacy of theby-pass in diverting atmospheric strays, and makes it possiblerto reducethe/ number of bafiie elements and by-pass ele-x ments. y

The vimprovement of the presentinvention l,still furtherincreases theefficacy of the ap tparatus, particularly 'in the very difficult featureof eliminating the' most persistent type' of s'trays, namely, thosesudden transitory impulses of large intensity and very short duration,which produce what,` are commonly yca-lled clicks or crashes by radiooperatprs. Strays of .this type are diiicultto eliminate, irst, becauseof .their relatively large amplitude, and second, because of theirabruptness and short duration. so vnois as the lessintensegrindingstrays,

While not they 'are far more ditiicult'to control because of theirproperty of lexciting shock oscilla` tions in a tuned'ci'rcuit,irrespective ofitS frequency.

By the use of the present invention this."

tendency to shock oscillations is rendered-innocuous, and the apparatusisA greatly simpli-- vfied. I' have found that in a suitably-designedsystem embodyingl the present invention, a single baffle element and asingle'in tensity selector are sufficient, thoughadditional 'baflieelements and by-pass-elements.. I'

' I n the presentinvention I take advantage .of the 'fact that' strays,particularly those of may obviously be employedif desired.

the character referred to, produce shockl oscillations inY the'systemand by so arrangimgz;

the apparatus that the shock .oscillations so .100

set up shall be of a different frequency from the signal oscillationsand providing means whereby suchv shock oscillations 'of differentfrequency may be separated from the signal oscillations,`-I am enabledin a very effective f way -to eliminate atmospheric strays.-

locsA y lhaving a capacity reactance.

In carrying out the present invention the shock oscillations of afrequency dierent 'from the signal frequency will be excluded cillationsof non-signal frequency may beaccomplished by partial de-tuniiig of someportion of the receiving system. One means of accomplishing this isfully described in an application for Letters Patent filed on even dateherewith Serial No. 315,650. By'

,means of the present invention, however, I am able to provide a channelfor converting and dissipating the energy of strays at nonvsignalfrequency withoutaifecting the tune .of the signal Vcircuit orimp-airing its resonance and selectivity. l

The means employed to accomplish this result preferably include areactive by-pass, whereby such shock oscillations as may be producedare. given a frequency different from the signal frequency, so that thebaffle circuit readily distinguishes between such.

shock oscillations and signal impulses, an intensity selector so relatedto the by-pass as to be peculiarly effective in absorbing the energy ofsuch shock oscillations and protect the baie circuit from excessivepotential-- differences, and a` baffle circuit of such stiffness orenergy storing capacity as to be highl eective'in excluding stiays,particularly tiiose of sharp intensity and short duration.

In the drawings, Fig. l shows an einbodiment of the invention as appliedto an ordinary receiving antenna, including a by-pass Fig. 2 shows anarrangement in which a loo'p collector is used, and including aninductive by-pass. Fig.l 3 shows an arrangement in whichthe by-passcontains both capacity and inductance. Fig. 4 shows a by-pass in whichthe `intensity selector itself possesses thel requisite capacityreactance. It shows also an application of 1the invention to currents ofaudio frequency. In all these figures, except Fig.-4, the intensityselector is inclicated diagraininatically, for the sake of simplicity,as a circle marked I. S. Figs. 5, 6, 8, 9, and 10 show various fforms ofintensity selector that may be employed in the various arrangementsillustrated in the foregoing diagrams. Fig. 7 is a typicalcharacteristic curve of ane form ofintensity selector.

In carrying out the present invention I utilize the fact that signalimpulses are -`periodic and, in the best modern apparatus,

sustained over a considerable number of oscillation periods, even insystems employing damped wave radiation, whereas the masacre strays thatare most troublesome are of very' short duration, and their energy isusually concentrated -in a single impulse or at most iii a stronglydamped wave.. The receiver oscillations produced by. signal waves aretherefore .the result of` repeated increments of energy from thesuccessive signal waves, which produce a cumulative eect in building upan oscillation in a tuned'receiver circuit. In the case of impulsivestrays, on the other hand, practically the entire energy is concentratediii'a single impulse. To aid in discriminating between these differenttypes of impulses I employ a baffle oircuit haring a` large energystoring capacity compared to that of the collecting system, so that theenergy taken up by the collector from a transitory stray impulse willhave 'a relatively small effect on thebaffle circuit, while the energyof a' signal impulse, being distributed over a. 'number of successivewaves, produces a relatively large comulative effect. y With such akbaille circuit I combine a by-pass element having a reactance that isvsmall compared to the reactances of the baiilc circuit,'and so does notappreciably affect its period of oscillation, but `which lissufiiciently .large with respect to the reactances of the collectorsystem to modify the ,natural frequency of this system, making it, withthe by-pass reactance included materially different from that of thebaiiie cir-l cuit. The energy taken up from a strayimpulse thereforewill be sliunted 0H through the by-pass where it will expend itself inoscillations of a frequency different frompurpose being so to adjust theantenna that the points a, b, shall be points of small potentialdifference at the ,signal frequency. A baffle circuit is connected atthe pointsv a, b, and includes the baffle elements T,.T, each comprisingan inductance L, L, and a capacity C, C', together with the priy mary pof a coupling` transformer p, s, whose secondary is included in thereceiving circuit proper. The receiving circuit is shown in simpleconventional form including an -oscillation capacity Cr and a detectorD,

which may be of any desired type, it being understood that itis not thepurpose ofthe present invention to set forth any particular form ofreceivercircuit or detector. AThe baffle circuit is tuned to thesignalfrequencyv and it is preferablymadeI symmetrical, the inductance -L andcapacity C being similar respectively to the inductance /and capacityC', though a single in ductance and a single capacitymay be employed ifdesired'.

rillhe inductance and capacity reactances are made large at the signalfrequency, so that the baflie circuitis a stiff oscillator, having' alarge energy storing capacity compared tof that of the collectingsystem. Since the collectingv system and the balile circuit are1ndependently tuned to the signal frequency,

the pointsa, b, will be points of small potential difference at thisfrequency, but will be points of large potential difference at any otherfrequency. Across these points a, b, is shunted a by-pass element whichis here shown as' comprisinga capacity S and an intensityselector I. S.rlhe reactance .of the by-pass is made small with respect to .the

inductance-and capacity reactances of the baiiie circuit, so that itdoes not appreciably affect the' natural period or impair the sclectivitof the latter. I t is, however, sufficiently arge with respect to thereactances of the collecting circuit to ,give the system A, Lr, a, S, b,a natural frequency of oscillation materially different from the signalfrequency.;

The operation of the apparatus `is asl fol-l' lows: A signal impulseimpingi-ng o n'the collector will set up oscillations of signalfrequency in the circuit A, Lr, a, T, p, T', b. Since the capacity andinductance reactances are all balanced at`the signal frequency the totalimpedance of this circuit will therefore be simply the 'equivalentresistance of the system. Hence. signal 'impulses will pass throughAitfreely, and the current will reach a considerable magnitudenotwithstanding 'the large renergy storing capacity of the system,because ofl thecumulative action of the successive waves." l'Since thebafie circuit and the collector., -circuit are individually tuned tothesignal frequency, the potential "difference between the points a, b,will be simply that required to overcome the 'equivalent resistance ofthe baffle circuit and receiving system. Since the impedance of theby-pass across the points a, b, is largawith respectto this equivalentresistance there forms a path of relativel high conductivity under theinfluence lof t is potential differwill be no material shunting ordiversion of signal energy.' f An impulse of other than signal frequencyimpinging 'on the antenna will encounter a large unbalanced reactance inthe baiiie elements T, T', which will`make thepoints a, b,- points ofrelatively ylarge potential difference 'and the stray .energy will be4diverted .to ground partly through the` reactiveA element of theby-pass"I S, but mainly through the intensity selector I. S., which Astrayimpulse of sudden andtransitory character vcommunicates energy tothe co1- 'ductance lector which expends itself through the bycircuitincluding the elementsv T, T, the

tendency for current to escape through the latter willbe small. Thistendency is still further reduced by the operation of the intensityselector I. S. The stray energy passing through Athe reactive by-pass Swill set up a potential difference across itsterminals. Since thevreactance lof Sv is material with respect to the other react'ances ofthe collector circuit, this potential difference will be sufficient tooperate the intensity selector even though the intrinsic energy of thestray is small. The intensity selector 1n co-operation with itsassociated elements,

especially the by-pass reac-tance S, thus acts v preferentially indiverting, not only powerful strays, but also s trays of much smallerenergy than that of signal limpulses which are not diverted. e!

The principles ofy operationV which cliari acterize the simplearrangement of .F ig. may be embodied in a variety of different forms ofapparatus. For example, Fig. 2 shows-an arrangement in which a loop col-'.lector A is used in place of the simple an tenna of Fig. l. Theinductance of this loop is balanced at the signal frequency bycapacities C1, Cl. The baiiie circuit, and thereeciver circuit shown-diagrammatically4 in its simplest form, are similar to those ofFig.. 1. The by-pass S is here shown as having an inductance reactance'instead of the capacity reactance shown in Fig. 1. The

reactancesof the collector A and capacities C1, C1 are small withrespect 4to the reactances ofthe baffle circuit as above outlined.

The collector is preferabl grounded at its middle point G, to avoidisturbing electro- Static effects. The.' operation of this ar` rangementis similar to that of Fig. 1. The

'frequency of shock oscillations will however be lower thanthe lsignalfrequency instead ofhigher, since the bypabs contains an ductanceinstead of a capacity. I It will bereadil understood that the totareactance of the y-pass may be made up partly o fa ca acity and partlyvof an in- Suc an arrangement is shownin Eig'. 3, where the by-pass Sincludes an inductance L, and a capacity C... The in- I ductance andcapacity should be so chosen that theircombined .reactance vis not zeroat the signal frequency, but either the capacityfor inductancepreponderates. The resultant rac-tance should`be large with respect tothe equivalentresistance of thelbaiie circuit but small with respect toits reactances, as` above explained.

sired value by suitably choosing` the size of' the electrodes; When' thepotential ditlcrence becomes great enough, however, to superpolarize thecell, its conductivity increases and it furnishes a by-pass of lowin'ipedance to such stronger impulses. Then the self-capacity ot thecell is utilized to furnish the bypass reactance, the choke.v

coils L.. should have preferably a large reactance. It' however theveffective capacity of the cell is negligible the coils Ls may beconstructed to have the desired induetance reactince; or a combinationot capacity and inductance reactances may beemployed to .produce thedesired reactive bypass clllect. Other forms oiE electrolytic cell usedas iii- -tensity selectors are set forth and described irl full in myPatent No. 1,407,109, above mentioned.

,y The arrangementot1 Fig. 4 includes also -an application of theinvention to currents of audiotrequency produced by passing the signalcurrents throughfa detector. The type ot detector here shown is atliermionic bulb D connected across the capacity Cr ot the receivercircuit in the usual way. is a local oscillator or other source ofalternating currentjof frequency slightly' ditferent from the Signal'frequency which is used in the/.reception o'faindainped waves `by the-beats\inetl iod. Then spark signals' are being `received the localgenerator O y is not required. It will *be understood that thedetector'D may be made self-oscillating in the well known way, in whichcase also the separate oscillator 0 willv not be required. The anode.circuit of the detector includes the primary pa of a Atransformer pa, sawhereby the audio frequency currents are applied to a baillecircuit'inclutling vthe inductance La, La and the capacity Ca. Theinductance of the secondary sa is balanced by the capacities C5, Us',making` the points a, b, points of small potential difference at thesigna-l audiov frequency. A by-passSn and intensity selector I. S. areshunted across the points a, lb. The capacity Ca of the baille circuitis inserted for convenience between thehalves of the primary pt of vthetelephone transformer pt st.

It will be noted that when operating on audio frequencies theelectromotive element,

'through which signal energy as Well as stray .cathode 7;.

raam-7s through the transformer para to the ,anode ot the detector. Theterm electromotive element as'used herein includes broadly means wherebythe e-lectromotive impulses are communicated to the rest of theapparatus.

noirsignal impulses.A

In Figs. l to et, inclusive, the intensity selector, connected acrossthe points (i, b, isA

indicated diagrammatically by a circle marked I S, to avoid unduecomplication ot' the diagram. There are a number of forms of intensityselector that may be used effectively' in these lvarious arrangements.Several of thesey are shown in Figs. 5 to 9 inclusive. .In each of thelatter dia'- grains the letters a, b, indicate the points of connectionwhereby the selector may be introduce-d in the circuit arrangements ofFigs. l to Ll at the points correspondingly marked.

i In my Patent No. 1,407,103, Iv have described and illustrated severalforms of'intensity selectors comprising electrolytic cells, eitherlsensitized by a polarizing battery, 'er used without initialpolarization. In Fig-4C ot' the present case I have illus- The wordbaille-element as used herein includes broadly means oilieringdiscriminating opposition to the passagev of,"

tra'ted another Aarrangement that I have found effective, including asingle cell hav.- ing two small aiiodes a', i and a commony The anodesare polarized to a point near the critical point by a-battery B adjustedby the potentiometer P. Short circuiting of the cell is prevented bychoke coils LS, whose impedence -may be made so large that it does notmaterially modify the apparentcapacity reluctance ot the cell,`or

otherwise adapted to the cell reactance, as.

already explained. Then the anodes z', z"

are connected across the points a., b, any difference ot' potentialwill, tend to superpolariz/,e one or the other ot'the anodes, causingthel conductivity of the cell to increase and act aS a by-pass.

Another arrangement of electrolytic cell that I have found ell'ective isshown in Fig. 5. I-Ieietwo cells S1, S2 are employed, having smallelectrodes, which are. rendered asymmetrical by polarization set up bythe. battery Ba through the potentiometer I?. The middle point of thebattery is connected to the point 5andthe junction point of the twocells hto the. point a. The cells are thus polarized in opposite-sensesso that they act potential difference across the terminals will tend tobreakl down one or the other cell.' i

There are many other devices besides electrolytic cells which possessthe intensity selective property. For example, lcertain forms of crystalcontacts, such' as carborundum, silicon, etc., while not showing thesharply defined critical point of the electrolytic cell, neverthelessshow a decided increase in conductivity with increasingpotentialdiiferences, particularly if sensitized by a local electromotive force..

conductivityby the use of large contact surfaces. l l

Fig. 6 shows a typical arrangement using crystal contacts. S1 and S2 arethe contacts, connectedjinopposite senses with 'relation 'to the-pointsanhand Ba, B.,v are their respective 'polarizing"batteries', and P1 P2adjusting potentiometers. The `by.pas's reactance is again shown at S.

A device that I have found sitive and effective as an intensity selectoris a thermionic valve4 properly constructed and opera-ted, and.comprising a hot cathode, emitting'electrons, and a` suitable anode,enclosed in a sealed container. lI prefer to use a bulb containing acertain amount of residual gas, aggon being preferable because offitsArelatively low ionization voltage,"the high conductivity which itimparts to the bulb. and the verysharply defined critical point of itscharacteristic. When an -electromotive force below a given value isapplied 'to the bulb only a very minute current iiows,

but when this electromotive force reaches a certain definite value thecurrent increases enormously and the conductivity of the bulb becomesrelatively very high. .By adjusting the electromotive force of the.sensitizing battery BBL to a point'just below this critical pointthedevice becomes an exceedingly sensitive intensity selector, and avery .small `4additional electromotive force applied Such c ontacts maybe constructed with fairly high'v peculiarly senpart of the curve isomitted in t-he figure. This characteristic makes such a bulb a highlyetlicie'nt intensity selector.

Fig. 8 shows a typical circuit arrangement of such a selector. The twoselector bulbs S1, S2 are Aoppositely connected, eachin series withabattery Ba with suitable adjustingl -means, whereby the potential`difference ismaintained justbelow 'theicritical point of tl'cu'rvey`Under some conditions the bulb has a negative characteristic above thecritical point, in whichcase it is desirableto use a. positiveresistance R1, R2 in series with it, to prevent instability. By suitablyadjusting this resistancethe apparatus. may lbe made highly sensitive tosmall voltage increases antd at the same time-possessing adegree ofstability which causes it to return at once-to its normal condition whenthe excessvolt-` age is removed;v

In some cases it is desirable to shunt the battery B.,L and'resistanceR1 or R2, in wholeo'r in part, by a condenser Cx shown.

l/Vhil'e I donot wish to confine myself to .90 any theoryl of operation,-it may be explained that on low voltages the conductivity of the bulbvis due almost entirely to electrons emitted by the hot cathode. 4Whenthe applied electromotive force reaches a certainy critical lpointhowever the velocity attained 'by"th'ese electrons becomes great enoughto ionize the gas, setting free both negative and positive ions in largenumbers, thus partially neutralizing the space-charge effect of the.negative' electron cloud and greatly int creasing the conductivity'otthe bulb.

The Vpoint' at which this ionization by col- AHsienoccurs and the extentof the ioniza-` tion `depend upon the nature of the gas` and itspressure, In the case of argon the critical electroinotive force is inthe neighborhood ofliivlts. l

his arrangement is exceedingly sensi-- tive, and requires care inproportioning the various constants of the system to obtain the lhighest sensitivity Without instability.

- Another arrangement is shown in 9, in which the selector bulbsl S1, S2are connected across 'the baffle circuit points a, b, with theirsensitizingl batteries. and potential adjusting means B... ResistancesRs, R, are shunted across each-'selector and sensitizing battery, theseyresistances being designed topermit the flow. of the requisite smallvsensitzingcurrent While preventing an excessive rush of current from thelocal j battery when .the selector is rendered highzly conducting by a.stray impulse. The mag- 12k nitude of the resistances-depends upon theparticular selector used and the sensitivity desired. Thereactiveby-pass S here shown is a, condenser, and in additionthe'stopping condenser Cx isdesirable, though not neces.-

sary, to `permit independent adjustment of the selectors.

By suitable proportioning 'of the resisty ances and of the sensitizingelectromotive force the sensitivity and conductivity of the bulb may bevaried over Wide limits. The temperature of the filament also has alarge influence on the properties of the bulb. By-

suitably correlating these various factors.

almost any desired characteristic of the selector may be secured.

Fig. l0 Ashows an. arrangement in which three-electrode thermio'nicbulbs are used,

the control electrode of each bulb G1, G2 being connected across lthesecondary ss of a battery Il...

transformen-of which the reactive by-pass sp is'the primary. The mainanode 1, c', and hot cathode 76 7c, are connected across the linedirectly, or through. a sensitizing When shock oscillations occur in theby-pass primary Sp, they induce an electromotive force in the secondarySS Which operates the control electrode to increase the conductivity ofthe bulb, which thus diverts the stray energy from the baille circuitvand limits the potential difference control anode battery Ba. may beemployed across a, b. i In this arrangement. as'in the arrangement ofFig. 9, I prefer to use selectors containing a lcertain amount of` gas,

referably argon, to increase the conductivity and theA sharpness ofr theselectivity. Either the main anode'lbattery Ba or the to produce thecritical potential difference in the bulb, so that a very slightadditional potential applied to the control electrode will cause a largeincrease in conductivity. Having now described my invention What I claimand desire to secure by lLetters Pat- (sol l. In 'a receiving system forradiant energy, an electromotive element, a bathe element timed to thesignal. frequency, by-pass means including a rcactance and an `intensityselector cooperating to divert preferentially. 'stray energy from thereceiving system and a receiver associated with the baffle element,substantially as set forth.

2. In a receiving system lfor radiant er.-`

ergy, an electromotive element, a baffle elcment timed to the signalfrequency, a bypasselement-having an impedance that is small Withrespect to the reactances of the baffle element, an intensity selectorassociated With said impedance and a receiver associated with `thebaffle element, substan-A tially as set forth.

3.A In a receiving system for radiant energy, a'n electromotive element,a baffle element tuned to the signal frequency and having large capacityand inductance reactanices compared with those of the electromotiveelement, a by-pass element including 'an intensity selector and havingan impedance that is small with respect to the reactances 'of the baffleelement, and a receiver associated with the baiile element,substantially` as set forth.

4. In a receiving system. for radiant energy, an electromotive element,a receiver, a baiie element between. the electromotive element and thereceiver having a large'energy storing capacity compared tothat of theelectromotive element, and a by-pass element acting preferentially todivert from lthe receiver and dissipate the energy of strays applied tothe electromotive element but not to divert signal impulses,substantially as. set forth.

5. In a receiving system for rradiant cnergy, an electromotive element,'a baffle element tuned tothe signal frequency, and a by-pass elementincluding an intensity selector Xhaving With the electromotive element anatural oscillation frequency differentA icc alone` While itsassociationwith the baffle*- element does not materially aect thefrequency of the oscillating system including the baffle element,substantially as set forth.

7. In a receiving system for radiant energy, an electromotive elementand a receiving oscillating system includinga baille element tuned tothe signal frequency, a bypass element having its'electrical constantsso chosen lwith respect to the constants 4of the electromotive elementand the baie 'element that its association With the electro- 'i motiveelement produces an oscillating sys,-

tem of a frequencydiiferent from Vthe natural frequency of theelectromotive elementl alone, While its associationv Withthe. bafileelement doesfnot materially affect the frequency of the oscillatingsystem including the baffle element, and an intensity selector'associated with the by-pass element, substantially as set forth.

8. In a receiving system' for radiant energy, an electromotive. element,a bae `element tuned to thesignal frequency having reactances that arelarge compared to those of the electromotive element, a b'y-pass elementhaving a reactance that is small 'coinpared to those of the baffleelement but material compared to those of the electromotive element,substantially as set forth '9; Ina receiving system for radianten--ergy, an electromotive element, a baffle element Atuned tothe signalfrequency. having reactances that are. large compared to those of theelectrornoti've element, `1a .by-pass .element having a reactance thatisfsinall compared to those of the baiile'element but material 'comparedto` those ofthe clectromol tive element, andan intensity selectorasso'-` ciated with Vtheby-pass element, substan-` f tially. as setforth.

10. In a receivlng-,systein forradiant energy, an elec-tromotiveelement,a baffle ele- "ment tuned to the signal frequency receivingv signalenergy from the electroinotive element, Ameansv associated with the'electromotive element vfor converting the energy of strays intocurrents of non-signal frequency, and means acting preferentially Vonthe currents of non-signal., frequency for dissipating the .strayenergy'. l f 11. In .receivingIsystemAfo-r radiant e`ni' ergy, anelectromotive element tuned to the signal frequency, ra baffle elementalso tuned to the signal frequency, receiving signalenergy fromthe'electromotive element, fmeans associated with the electromotiveelement for'convertingtheenergy of strays into currents of non-signalfrequency, and 'means actingpeferentially on the current 0fnon-l signalfrequency for dissipating the s tray energy.

motive element for converting the energy' 12. Ina receivingsystemforradiantenergy, an electromotivelelement,1-a baille element tuned to the`signalv frequency, receiving signalv energy from the electromotiveelement, means'associ-ated 'with theelectro-v of straysinto currents ofnon-signal fre-r quency, and intensit "'selective means asso# ciatedtherewith and adapted to divert such converted `stray energy.

13. lIn a receiving system for radiantV en.- ergy, an electromotiveelement tuned .to the signal frequency, a baffle element also -uned tothe' signal frequency receivingsignal energy from the electromotiveelement, means associated with the electromotive v element forconverting the energy of strays into'currents of non-signal frequency,"and intensity selective means associated therewith adapt-V ed todivertsuch converted stray energy.

14, In a receiving system for radiant en ergy, an electromotive elementtuned to the signal frequency, a baffle element also tuned tothe signalfrequency but having a stiff oscillation charagteristic compared withthe electron'iotive element, a by-pass element having its electricalconstants so chosen with respect to the constants of the electromo'tiveelement and the baffle element that its asso-- ciation with theelectromotive element produces an oscillating system of a frequencydifferent from the natural frequency of the to the signal frequencyassociated therewith y and having large capacity and ,inductancereactances compared with thbse of the' first tuned elemenna by-passelement of small l impedance compared tothe reactances of thel secondelement and connected thereto at pointsof small potential difference atthe signal frequency, substantiall as set forth.I

16. In a'receiving system or radiant en` ergy, a tuned element. tuned tot hesignal frequency, a second tuned element also tuned to the signalfrequency associated therewith and having large capacity and inductancevreactances compared with those of thefirst tuned element, a reactiveby-pa-ss element of small inpedance comparedto the reactances ofthesecond element and connected thereto at points-of small potential4difference at lthe signal frequency, substantially as 'set-- v17. In areceiving system for radiant env-i.`

ergy, an electromotive element tuned 'to the signal frequency, a baffleelement also tuned to the .signal frequency associated therewith n andhaving large capacity and' inductance reactances compared with theelectromotive element, a reactive by-pass elementincluding an intensityselectorconnected between the electromotive element and the baflieelement at points of smallpotential difference at the sign-a1 frequency,subs'antially as set forth.- 'Y

18;' The 4method of selectively receiving radiant energy which consistsin receiving the energy of'signal frequency, converting v stray energyinto 'oscillations 'of non-signal vfrequency and' diverting anddissipating this converted stray energy by preferential selection of itsnonsignal frequency, sub-l stantially as set forthu l19..'I`he method ofselectively receiving radiant energy which vconsists in receiving theenergy'of signal' frequency, convertin stray energy into oscillations-of non-signa frequency and diverting and'dissipating by intensityselection this 'converted stray energy, substantially as set forth.

20. The method of selectively receiving radiant energy-which consists inreceiving the energyof signal frequency, converting stray energy intooscillations of non-signal frequency and selectively dissipating thisconverted energy by intensity selection acting preferentially on itsnon-signal frequency, and receiving the undiverted signal energy,substantially as set forth.

21. In areceiving system-for radiant energy, an electromotive element, abaffle element tuned to the signal frequency f and.

ment tuned tothe signal frequency and having reactances largewithrespect to the reactancc of the electromotive element, airintcnsityselector lconnected between the electromotive element and the bailleelement` at points of small potential difference for signal impulses butlarge lpotential difference for strays, substantially as' set forth.

' 22. In a receiving systemA for radianten-` ergy, an electromotiveelement, a baille elehaving reactances large with respect. to the`reactance of the electromotive element,va

reactive by-pass element including an in-v tensity selector connectedbetween the collector element and the baille element at points of smallpotential difference for signal impulses but large potential differencefor strays,.substantially as set forth.

23. Ina receiving system for radiant energy, an electromotive element, abaille elementv tuned to the signal frequency and having reactanceslarge with respect to the reactance of the electromotive element', abypass element including an intensity selector,

having .a small impedance relative to the reactance of the bailleelement, connected Vat points of smallpotential diiferencefor signalimpulses but large potential dierence for strays, substantially as setforth.-

24. In a receiving system for radiant en-l ergy, an electromotiveelement of 'high elec-I trical mobility, a heavily loaded baille elementtuned to the signal frequency associated therewith, and al by-passelementacting preferentially to divert from the baille elementstray"impulsesrcceived vby'the electromotive element, substantially asset forth.

25. In a receiving system for radiant en- 1 ergy, anelectromotiveelement of high electrical mobility, .a heavily loaded-4bafl'le clement tuned to the signal frequency associated therewith, andaby-pass element acting preferentially to divert from-the baillevelement stray impulses received bythe ele'ctromotive element, andincluding an intensity'selector, substantiallyas set forth.

26. In a receiving system for radiant energy, an electromotive elementof high electricalA mobility, a receiving oscillating system including aheavily loaded baille element tuned tofthe signal'frequency associatedtherewith, anda by-pass elementl having its electrical constants sochosen lwith respect to' the yconstants of the electromotive element andbaille elementl that its association with" the electromotive elementproducesan oscillating system of frequency differentY from the naturalfrequency of 'the electromotive elementalone, while its association withthe baille element does not materially 'aifect the frequency'of theoscillating system including .the baille element, substantially as setforth.

27. In a receiving system'for radiant energy, an electromotive elementof high electrical mobility, a heavily loaded baifleelement tuned to thesignal frequency associ- -r fated therewith, a lay-pass element formingwith the electromotive element an oscillat- 4 ing system having anatural frequency for shock oscillations different from the signalfrequency while not materially affecting the natural frequency of theballe'element, substantially as setforth.

28'. In a receiving system for radiant energy, an electromot-ive elementofhigh electrical mobility, a heavily loaded baille element tuned to the'signal frequency associated therewith, and a by-pass element adapted todivert from the baille element and dissipate the energy ofstrayimpulses-at a frequency different from the signal frequency Whilenot'materiallyaffecting the selectivity ofthe baille element for signalimpulses, substantially as set forth.

29. In a receiving system for radiant energy, an electroi'notiyeelement,`a baille element tuned tothe signal frequency, a loypasselement not materially diverting signal impulses, but diverting'strayimpulses at a frequency different "from the signal frequency, and anintensity selector connected at points of small potential difference`for signal frequency but relatively large potential difference forstrays, substantially as set 31. In a receiving system for radiantenergy, an electromotive element, a bail'leele'- ment tuned to thesignal frequency, a reac- -tive by-'pass element not materiallydiverting signal impulses but diverting strayv im' pulses at afrequency-different from the signal frequency, Aand an intensityselector associated with the reactance of the by-pass,' and responsiveto the large-'potential diiference produced by 'strays` traversing theby-pass but not responsive to the relatively small poy tential1difference for signall impulses, substantially as set forth. 32. In areceiver for radiantv energy, a

complex oscillating system comprising a' rey ceiving portion responsiveto the signal frequency, a stra-y diverting portion having a pulses ofsignal frequency but less freely to different preferentialfrequency, andan intensity selector co-operating with thefrequency selective elementto guard ythe receiving portion preferentially against stray inipulses,substantially as set forthf* In a receiver for -radiant energy, acomplex oscillating systemcomprising a re-- ceiving portion having vasti oscillation characteristic at the signal frequency, .a more mobileportion having a different oscillation frequency, andan intensityselector guarding the receiving portion, substantially as set forth.

34. In a receiving system for radiant eng ergy, an electromotiveelement,-a'1 feceiv ing element responding freely to sustained im-lother impulses, a stray dissipating element oscillating preferentiallyat ,a different frequency and an'intensity selector co-operating withthe frequency selective element to guard the receiving portionpreferentially against stray impulses, substantially as set forth.

35. In a receivingsystein for radiant energy, a mobile, electromotiveelement, a heavily loaded rec/eiving element, a stray dissi-4 patingelement includinga reactance associated with the electromotive elementand by this association modifying the frequency responsiveness of theelectromotive element while not materially affecting the frequencyresponsiveness of the receiving element, substantially as set forth. 36.In a receiving system for radiant energy, a receiving element responsiveto sustained signalY impulses but sluggish-in Vresponse to shocks, amobile shock absorbing clement associated therewith and an intenyverting circuit of noni-signal frequency, and

` stantially as set forth.

intensity selective meansfor guarding the signal circuit against. strayimpulses, sub

,39. In a receiving system for radiantJ v.energy, an electromotiveelement, a receiving element responsive to impulses of signal frequency,means for converting the energy of: strays into oscillationsl ofnon-signal frequency, and means for limitin the intensity of non-signalimpulses applie to the receiving element, substantially as set forth.

Y 40. In a receiving system for radiant energy, anelectromotive element,a receiving element responsive to impulses of signal frequency,.means\for converting theV energy of strays into oscillations of non-signalfre-y quency, and means. for selectively limiting the intensity ofnon-signal impulses applied to tlie receivingelement, substantially asset forth.'

41. In a receiving system 4for radiant energy, a receiver responsive tosustained impulses of signal frequency,means 'for converting shockenergy of strays into-'oscillations of non-signal frequency, a frequencyselective element tuned to signal frequency, and an intensity selectivemeans co-operatthe non-signall impulses, substantially as set forth. 'i'

42. In a system for separating mingled electrical impulses, an intensityselector comanode and an incandescent cathode and contains anionizablegas, and means for apply- `ing to the valve a sensitizing voltage justbelow the' critical potential required to produce gas ionization, meansfor superimposing on the sensitizing voltage' the mingled electriv calimpulses, and\means cooperating withtlie intensityl selector fordiscriminating between andy separating the mingled electrical impulses.

43. In 'a system" for separating mingled electrical impulses, anintensity selector coin-4 pr-ising a thermionic valve, which has ,an

anode and an incandescent cathodepand con-- prising a thermionic valve,which `has an.`

tains an ionizable gas, land means for aps plying to the valve avsensitizing voltage .just below the critical potential required toproduce vgas ionization, meansfor superimposing on tliesensitizingvoltage themingled' electrical impulses, and vmeans cooperating with theintensity selector to enhance the intensity selective property thereofand to receive desired impulses while rejecting undesired impulses.

44. Inan intensity selectorl for yelectrical impulses a thermionic'valve having a sharply inflected current-electromotive forcecharacteristic, a source of electromotive force for sensitizingtheselector to or near the critical point, means for superimposing omthesensitizing electromotive force the impulses to be selectivelytransmitted, andnieans-for preventing an excessive rush of current fromthe sensitizing source when the critical point is passed, substantiallyas set forth.

45. In a receiving system for radiant energy, an intensityselectorcomprising athermionic device including a source of electronsand an ionizable gas, means for applying to the device a sensitizingelectromotive force below the point of extensive ionization, a.. controlelectrode whereby impulses to be so ing therewith to guard the receiveragainst4 selectively conducted produce gas ionization and cause a. largeincrease in conductivity of the-gaseous medium, and a third electrodewhereby this conductivity is utilized for the 5 selective conduction ofthe impulses which causes the increase in conductivity, substantially asset forth. v

this second ,day of August, 1919.

FREDERICK K. VREEI-JAND. v

Witnesses:

FRANK L. DYER, C. JORDAN.

